悬臂大直径薄壁筒桩在深厚软土地区浅基坑支护中的应用

Application of Thin-Walled Large Diameter Reinforced Concrete Cylindrical Pile as Deep Excavation Cantilever Supporting Structure in Soft Soils

针对深厚软土地区的浅基坑,设计一种既安全又经济合理的支护方式是众多工程师关注的焦点。以温州地区某一实际工程为依托,从设计思路、计算和监测等方面对深厚软土地区的浅基坑支护方案进行了系统分析。研究结果表明:(1)在因周边环境和场地施工空间受限等因素导致放坡开挖和锚杆/索类等支护方案无法实施的情况下,悬臂大直径薄壁筒桩支护方案较其他支护方式具有工期短、控制变形能力强和经济效益显著等优点。(2)岩土工程师不能简单地根据规范计算出来的位移总量来评价某个支护方案对位移的控制能力,应结合预估的基坑施工时间,按照每天蠕变一定的量来推算一个预估位移总量,且该值应控制在周边环境能承受的范围之内。(3)在深厚软土地区,基坑周边的坑中坑(电梯井)开挖对支护结构安全影响明显,若设计的基坑支护深度未考虑其影响,则易产生安全隐患。

Selection of a cost effective and safe supporting structure for the deep excavation in soft soils with relatively shallow depth is critical to the foundation cost control.The supporting structure selections of sallow excavation depth in Whenzhou soft soils are evaluated through a case history from aspects of design approach,analysis method,and construction monitoring.The following conclusions can be presented:⑴Thin-walled cantilever large diameter reinforced concrete cylindrical pile has the advantages of cost effective,short construction period,and good deformation control in the constraint space where the slope,or ground anchor cannot be applied.⑵It is inappropriate to estimate the total deflection only from formula in the code and the total deflection should consider the daily creep.Further,the allowable total deflection should consider the adjacent environment.⑶The deeper excavation such as the excavation of elevator shaft,has the obvious adverse effect of the safety of supporting structure.The supporting design of these areas should be specially considered.